The present invention relates generally to a conduit and more particularly to a heat insulated, high temperature fluid carrying conduit in combination with a specific pressure relief valve.
Where conduit service for carrying high temperature fluids, for example extremely hot water or steam, is required, it is often desirable and sometimes necessary to use a heat insulated conduit for this service. A quite satisfactory conduit of this type is disclosed in U.S. Pat. No. 3,563,572, issued to D. W. French on February 16, 1971, and assigned to Johns-Manville Corporation, Assignee of the present application.
The fluid carrying insulated conduit disclosed in the French patent is essentially composed of concentric lengths of pipe consisting of an inner fluid carrying pipe or core, an outer protective pipe or casing spaced concentrically around the inner pipe core and a layer of thermal insulating material positioned concentrically therebetween. Two conduit sections of this type are connected together by means of a composite coupling arrangement including an innermost tubular sealing sleeve or coupling which is positioned concentrically around adjacent end sections of the inner fluid carrying pipes or cores of adjacent conduit sections. An improvement in this overall arrangement is disclosed in United States patent application Ser. No. 557,704, filed Mar. 12, 1975, now U.S. Pat. No. 4,006,920, issued Feb. 8, 1977, to T. H. Sadler and R. N. Cerny and also assigned to Johns-Manville Corporation. As described in this application, this improvement is provided to prevent moisture from finding its way to the layer of insulation material through the coupling.
While the improvement as set forth in this patent has been found to be satisfactory for its intended purpose, moisture could possibly still find its way into the insulation layer. For example, while unlikely, the moisture might be present during initial formation of the conduit. In any case, by whatever means this occurs, if it occurs at all, the present invention, as will be seen hereinafter, is provided for passing this moisture to the ambient surroundings should such moisture be present and should it build in pressure within the insulation layer.